Process for cupric-oxide removal



Patented Aug. 19, 1930 UNITED STATES PATENT OFFICE WILLIAM THEODORE ANDERSON, JR., AND LESTER FLETCHER EIRD, OF NEWARK.

' NEW JERSEY, ASSIGNORS T0 HANOVIA CHEMICAL AND MANUFACTURING CO]!- IPANY, OF NEWARK, NEW JERSEY, A CORPORATION OF NEW JERSEY PROCESS FOR CUPRIC-OXIDE REMOVAL No Drawing.

This invention relates to a process for the removal of cupric oxide (black) from the surfaces ofcrystalline cuprous oxide or from the surfaces of metallic copper.

The removal of the black oxide can be accomplished by mechanical means for example by planing or cutting with abrasives such as emery cloth on cutting wheels but very often such methods are not desirable. In those cases where it is necessary to remove black oxide from the surface of red oxide it is very important that the red oxide should not be damaged or broken in any way. Since the black oxide is harder than the red oxide any device that will remove the black oxide will readily remove the red oxide as well. Our invention as herein described and defined in the appended claimsets forth a process which we have found to be very" desirable and effective in removing black cupric oxide from copper or cuprous oxide surfaces. This process will not produce mechanical damage, such as cracks or abrasions, to the under surfaces and will remove any thickness of black oxide ordinarily produced in the treatment of copper.

The cupric (black) oxide as formed on copper surfaces or on top of red oxide surfaces is of fine crystalline structure and is quite porous to liquids or gases. The red cuprous crystalline oxide on the other hand is attacked comparatively slowly by either liquids or gases. These characteristics are favorable to electrolytic methods of separation.

The electrolyte required by our process may be dilute sulphuric acid or other strong acid which readily attacks copper oxides. Any variety or concentration of copper salts may be included in the electrolyte. he copper plate covered with oxide is used for an electrode in this electrolyte and a piece of pure copper or chemically inert conducting substance for the other electrode. If direct current is passed through the solution in either direction reduction of the surface oxide occurs. If the oxide coated copper is made the cathode a deposit of metallic spongy cop er is formed replacing the reduced oxid d on the surface. Copper so Application filed October 28, 1927. Serial No. 229,524.

formed can be removed by reversing the direction of current flow. Alternating current is the more desirable electrical supply since by its use the oxide is loosened without any deposition of metallic copper. After several seconds of treatment the loosened oxide can be washed 03 leaving the under surface clean. Further action by the acid, after the cleaned surface is removed from the solution, is prevented by immediate neutralization with an alkaline substance, for example, dipping the cleaned surface in a dilute solution of ammonium h droxide.

The advantageso this process are many. First, a satisfactory simple cleaning method removes the need for special precautions to prevent the formation of the black oxide on the surfaces. Second, all parts of the process are simple requiring no special or elaborate equipment. Third, only the black oxide is attacked readily by this procedure, since the red crystalline oxide is only acted upon at a greatly reduced rate. Fourth, the black 0x1 ide is completely loosened from the surface so that it can be washed off entirely with a minimum of labor. Fifth, the concentration of electric current is not important and may vary- Widely. Sixth, the kind or type of electrolyte is not critical and many kinds and concentrations are suitable.

Having described our invention, what we claim as new and desire to secure by Letters Patent, is The herein described process of removing cupric oxide from a metallic copper and crystalline cuprous oxide surface, which consists lacing the object carrying the cupric oxi e into an electrolyte, said electrolyte being a strong acid which readily attacks copper oxide, passing an alternating electric current through the electrolyte to the cupric oxide as an electrode to thereby loosen the cupric oxide, washing off the loosened cupric oxide from the object, and then immersing the object in an alkaline substance to prevent further action of the acid.

This specification signed and witnessed this twenty-fifth day of October, 1927.

WILLIAM THEODORE ANDERSON, Jr.

LESTER FLETCHER BIRD. 

